REG NASA-LLIS-0867-2000 Lessons Learned Use of GN2 for Valve Corrosion Control.pdf

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1、Best Practices Entry: Best Practice Info:a71 Committee Approval Date: 2000-04-24a71 Center Point of Contact: KSCa71 Submitted by: Wilson HarkinsSubject: Use of GN2 for Valve Corrosion Control Practice: GN2is provided to the actuator breather of pneumatically actuated valves used in hostile environme

2、nts (salt spray, high humidity, SRB exhaust).Programs that Certify Usage: This practice has been used on the Space Shuttle Program and the KSC Launch Operations Area Hypergolic Servicing System.Center to Contact for Information: KSCImplementation Method: This Lesson Learned is based on Maintainabili

3、ty Technique number OPS-16 from NASA Technical Memorandum 4628, Recommended Techniques for Effective Maintainability.Attaching a source of GN2to the actuator breather provides an atmosphere in the actuator chamber of pneumatically actuated valves that prevents corrosion thus lengthening the life of

4、the valves.GN2is provided to the actuator breather of the pneumatically actuated valves.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The source may be a dedicated GN2source or a more efficient means would be to tap off a nearby panel that uses GN2

5、for an environmental or hazard proofing purge. A line connected from the panel to the actuator breather port would allow access to the GN2for filling the valve actuator chamber when the valve is deactivated (see Figure 1).refer to D descriptionD When designing the system, caution should be used to p

6、revent or minimize back pressure on the actuator which would reduce actuator performance.Impact of Non-Practice: When a pneumatically actuated valve is deactivated and the valve changes position, the valve diaphragm returns to the normal position and provides a vacuum at the actuator breather. This

7、results in the outside air being drawn into the actuator chamber, along with any contaminants in the air. At the Space Shuttle launch pads the contaminants that are in the air include salt spray, SRB exhaust, possible N2O4vapors, and water from high humidity. The contaminants cause corrosion in the

8、actuator chamber affecting the operation of the valve. Providing GN2to the actuator breather Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-eliminates the possibility of drawing contaminants into the chamber.Related Practices: N/A Additional Info: Approval Info: a71 Approval Date: 2000-04-24a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-